Trials on the N95 concluded that it didn't really do a good job filtering chemical pollution.
Hypothesis "To test if wearing the R95 Particulate Respirator face mask, produced by 3M reduces levels of pollution exposure biomarkers in 40 healthy volunteers." Tests were done in Hanoi, Vietnam, from July to October 2009.
The results: http://www.ncbi.nlm.nih.gov/pubmed/23013369
RESULTS: Forty-four participants (54.5% male, median age 40 years)
were enrolled with the majority being motorbike taxi drivers (38.6%)
or street vendors (34.1%). The baseline creatinine corrected
urinary level for 1-OHP was much higher than other international
comparisons: 1020 ng/g creatinine (IQR: 604-1551). Wearing a R95
mask had no significant effect on 1-OHP levels: estimated
multiplicative effect 1.0 (95% CI: 0.92-1.09) or other OH-PAHs,
except 1-hydroxynaphthalene (1-OHN): 0.86 (95% CI: 0.11-0.96).
CONCLUSIONS: High levels of urine OH-PAHs were found in Hanoi street workers. No effect was seen on urine OH-PAH levels by wearing R95 particulate respirators in an area of high urban air pollution, except for 1-OHN. A lack of effect may be de to gaseous phase PAHs that were not filtered efficiently by the respirator. The high levels of urinary OH-PAHs found, urges for effective interventions.